Article
Mechanics
Lianzhou Wang, Xinyu Liu, Nian Wang, Mijian Li
Summary: The wake instabilities of a propeller operating under turbulent-inflow conditions were studied using the improved delayed detached eddy simulation method, revealing the interaction between turbulence and tip vortices.
Article
Mechanics
Ke Zhu, Feng Xie, Gang Wang, Yan-chao Hu, Yan-guang Yang, Ming-bo Sun, Wei-dong Liu
Summary: The effects of a transverse jet on shock wave/turbulent boundary layer interactions at different distances are studied using large eddy simulation. The study examines the instantaneous characteristics of the turbulent boundary layer influenced by the wake of the jet, including streaks near the wall and large-scale vortices. The separation features are compared and analyzed through three-dimensional separation bubbles and skin frictions, revealing the influence of a far jet and a near jet on separation, reattachment points, and turbulent intensity.
Article
Mechanics
Hongyi Jiang, Liang Cheng
Summary: In this study, mesh convergence for Re=3900 was demonstrated using the Nektar++ model, comparing the computational efficiencies of Nektar++ and OpenFOAM. The computations were then generalized to a range of Re=400-3900, exploring the physical mechanisms behind the variations in wake recirculation length and hydrodynamic forces.
Article
Engineering, Civil
Henry Plischka, Simon Michel, Johann Turnow, Bernd Leitl, Nikolai Kornev
Summary: In this study, measurements and simulations were conducted to investigate the flow characteristics of the atmospheric boundary layer (ABL) with different ground roughness lengths. The results showed that the synthetic turbulence generation techniques were applicable to the LES of ABL simulations, leading to a significant reduction in the required inflow domain length.
JOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS
(2022)
Article
Environmental Sciences
Inanc Senocak, Rey DeLeon
Summary: The concept of buoyancy perturbations with colored noise is investigated to trigger turbulence in upstream flows approaching complex terrain regions for accurate turbulent inflow generation. The application of this technique in predicting winds around Askervein and Bolund Hills shows that a common value for the bulk Richardson number works well for various flow problems. Additionally, it is found that the height of the perturbation box plays an important role in the accuracy of predictions around complex terrain, with good results obtained when the perturbation box height is a fraction of the Obukhov length scale.
Article
Mechanics
Fei Li, Zhenguo Wang, Peibo Li, Mingbo Sun, Hongbo Wang
Summary: This study numerically investigates the gas-liquid mixing process of a liquid jet in supersonic crossflow. The simulation results show good agreement with experimental data, capturing the penetration depth and lateral extension width of the spray. The influence of counter-rotating vortex pair and horseshoe vortex on the transport process and formation of spray foot is systematically studied.
Article
Engineering, Civil
W. A. McMullan, M. Angelino
Summary: The influence of various tree planting configurations on tracer gas dispersion in an urban street canyon is numerically studied using OpenFOAM Large Eddy Simulation (LES). The results show that tree stand density affects pollutant dispersion, with tree crowns reducing the effectiveness of the canyon vortex in ventilating the street and enhancing pollutant concentration at pedestrian level.
JOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS
(2022)
Article
Thermodynamics
Aritra Roy Choudhury, Kameswararao Anupindi
Summary: Several industrial and engineering applications utilize ventilated offset-jets, such as flow separation control devices, upper surface blowing in aircraft, drying processes, and fuel injection systems. The design and efficient operation of these devices depend on controlling turbulence levels, heat transfer rates, and flow reattachment points. This study aims to analyze the flow and thermal characteristics of a planar turbulent offset-jet using large-eddy simulations (LES) for different ventilated-jet velocities.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2023)
Article
Energy & Fuels
Xianyin Leng, Yicheng Deng, Wei Guan, Weibo Xie, Zhixia He, Qian Wang, Xuesheng Yan, Wuqiang Long
Summary: A spirally grooved hole (SGH) nozzle was designed to enhance fuel atomization for diesel engines. Numerical results showed that the SGH nozzle can significantly improve jet breakup and produce finer droplets.
Article
Construction & Building Technology
Jun Wang, Li Wang, William(Wei) Zhang
Summary: The study focuses on turbulence energy spectrum of fluctuating inflow velocity in LES, proposing a projection algorithm to modify the previous spectrum method. The validated procedure showed better performance and revealed specific oscillation patterns in flow change rate around openings in building natural ventilation design.
BUILDING AND ENVIRONMENT
(2021)
Article
Thermodynamics
Achyut Panchal, Suresh Menon
Summary: Understanding combustion and flame stabilization of alternate fuels is crucial for their use in aviation. This study uses large eddy simulation to simulate a real gas turbine combustor and investigate the burning behavior and flame stabilization mechanism of two fuels. The results show that the flame anchor point is premixed, but most heat release comes from fuel pockets burning in a nonpremixed manner.
COMBUSTION AND FLAME
(2022)
Article
Mechanics
Lianzhou Wang, Wanzhen Luo, Mijian Li
Summary: This study investigates the flow physics in propeller wakes and finds that turbulent inflow significantly modifies the morphology of the vortex system behind the propeller, leading to instability and diffusion of primary tip vortices shed by the blade tips.
Article
Thermodynamics
Zhiyuan Zhao, Fengbo Wen, Xiaolei Tang, Yuxi Luo, Rui Hou, Zhongqi Wang
Summary: The study on film cooling with delta winglet vortex generator pair (DWVGP) shows that vortical structures have a significant impact on film cooling effectiveness in the flow field of a jet in crossflow (JICF). The DWVGP evolved anti-CRVP allows for earlier reattachment of coolant and achieves enhanced film cooling effectiveness in the spanwise direction.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2021)
Article
Mechanics
Prince Charles, Vagesh D. Narasimhamurthy
Summary: The effects of a pintle-shaped orifice on a planar turbulent jet flow at Reynolds number 4000 have been studied using direct numerical simulations. Flapping of the jet and low-frequency modulation of the KH instability were observed, as well as the presence of an oblique vortex pattern. The study also compared the near-field region influence on the far-field flow characteristics.
Article
Green & Sustainable Science & Technology
Ava Shahrokhi, Julien Berthaut-Gerentes, Lin Ma, Derek Ingham, Mohamed Pourkashanian
Summary: This paper validates the effectiveness and accuracy of using a reduced turbulence integral length scale for inflow generation in large eddy simulation (LES) and develops a technique to estimate the real local length scales using simulation results. The results show that there is an excellent agreement between the length scale from simulation and measurement when scaled with their corresponding freestream/inlet value. This indicates that a reduced integral length scale can be safely used for LES to provide reliable predictions for energy spectrum and length scales around complex geometries.
Article
Automation & Control Systems
Donggun Son, Haecheon Choi
IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY
(2019)
Article
Computer Science, Interdisciplinary Applications
Woojin Kim, Haecheon Choi
COMPUTERS & FLUIDS
(2019)
Review
Thermodynamics
Woojin Kim, Haecheon Choi
INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW
(2019)
Article
Engineering, Mechanical
Hongkwon Lee, Keuntae Park, Haecheon Choi
JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY
(2019)
Article
Biophysics
Woojin Kim, Hansol Lee, Jungil Lee, Daehan Jung, Haecheon Choi
JOURNAL OF BIOMECHANICS
(2019)
Article
Mechanics
Sehyeong Oh, Boogeon Lee, Hyungmin Park, Haecheon Choi, Sun-Tae Kim
JOURNAL OF FLUID MECHANICS
(2020)
Article
Engineering, Mechanical
Boogeon Lee, Sehyeong Oh, Haecheon Choi, Hyungmin Park
JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY
(2020)
Article
Engineering, Mechanical
Dongri Kim, Hyungrok Do, Haecheon Choi
EXPERIMENTS IN FLUIDS
(2020)
Article
Multidisciplinary Sciences
Woojin Kim, Haecheon Choi, Jihoon Kweon, Dong Hyun Yang, Young-Hak Kim
Article
Mechanics
Jonghwan Park, Haecheon Choi
JOURNAL OF FLUID MECHANICS
(2020)
Article
Mechanics
Jonghwan Park, Haecheon Choi
Summary: The study developed a subgrid-scale model using a fully connected neural network and conducted both a priori and a posteriori tests to evaluate its prediction performance. Results showed that while the NN-based SGS model can provide good predictions under certain conditions, it also exhibited stability issues in some cases.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Dohyun Jin, Zhi Wu, Haecheon Choi
Summary: This study proposes a predictive model for the drag coefficient of a circular cylinder based on the mean streamwise velocity and Reynolds normal stresses in the wake, which shows good agreement with numerical simulations across various Reynolds numbers.
Article
Mechanics
Zhi Wu, Haecheon Choi
Summary: Steady discrete blowing is more effective for drag reduction than steady uniform blowing, with a maximum drag reduction of 38%. Time-periodic uniform blowing is more effective than steady discrete blowing, with maximum drag reduction of 68%. Different vortex lock-on phenomena play a significant role in drag decrease and increase during time-periodic blowing.
Article
Mechanics
Daeun Song, Woojin Kim, Oh-Kyoung Kwon, Haecheon Choi
Summary: We conducted a direct numerical simulation of the flow over the Tacoma Narrows Bridge to reproduce the vertical and torsional vibrations that occurred before its collapse in 1940. The simulation used real-scale structural parameters and modified the fluid property to provide realistic aerodynamic force and moment. Through the simulation, we observed vertical vibration resulting from vortex shedding frequency lock-in, followed by exponential growth of torsional vibration due to aeroelastic fluttering. We also investigated the roles of free-stream velocity and vertical vibration in the growth of torsional vibration.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Sangwoo Ahnn, Haecheon Choi
Summary: Numerical analysis is conducted to investigate the aerodynamic performance and characteristics of flow around a simplified vertical-axis wind turbine (VAWT). The primary flow feature observed is the formation and evolution of leading-edge vortices (LEVs) at lower tip-speed ratios, which have a notable impact on the power coefficient. A modified tip-speed ratio allows for the representation of flow structures with different tip-speed ratios and number of blades. The time-averaged power coefficient is a function of the modified tip-speed ratio, and its maximum value occurs at a specific range of the modified tip-speed ratio.